R Raw Paths, DP4 Style

A couple of months ago, I wrote about raw paths and ���all files access���
on Android R, using R DP2. And��� what I had there on raw paths is not completely
accurate for R DP4. I am not certain how much of that represents changes in Android R and how much
of that represents screwups in my original testing.

What I am seeing in R DP4 is:

With no permissions, your app can create files of any type in the Documents/ and Downloads/
directories. Your app can then manipulate those files afterwards.

With READ_EXTERNAL_STORAGE permission, your app can read ���media files��� in any directory
other than Android/. The precise definition of ���media files��� is indeterminate. More
on this later.

Whether files can be read will depend on whether they are indexed by the MediaStore.
So, for example, files that you push up using adb push will not be visible until
sometime after MediaStore indexes them (e.g., after a device reboot).

No additional abilities appear to be gained by holding WRITE_EXTERNAL_STORAGE
(as expected) or having a targetSdkVersion of R.

The second bullet lines up with the minimalist documentation on raw paths,
which states:

Android 11 allows apps that have the READ_EXTERNAL_STORAGE permission to read a device���s media files using direct file paths and native libraries.

(emphasis added)

The definition of ���media files��� is murky. It appears to be tied to MediaStore
indexing, not just file extensions. So, with READ_EXTERNAL_STORAGE:

We can read PNG files

We cannot read text files

We cannot read text files with a .png extension

We cannot read text files created by an app in Documents/ or Downloads/, even
though those apps were able to create the files directly in those directories

We cannot read PNG files that were put on the device that MediaStore does
not know about yet (e.g., the adb push scenario)

So, media file formats that MediaStore does not know about might not be accessible
this way, even if you and your users think of those formats as being ���media���.

If your app is mostly focused on media, this situation may be an improvement
over what we have for Android 10. But, given the undocumented definition of
���media files���, I would be somewhat hesitant to rely upon it.